Preheat oven to 350F.
 

Heat oil in a saucepan over medium heat and sauté the onion, garlic and ginger until the onions are golden brown. Add the orange juice, 1 cup of brown sugar and simmer until the liquid reduces by half. Add the mustard and season to taste with sea salt and freshly cracked black pepper. Take off the stove, purée with an immersion blender and set the glaze aside.
 

Score the ham diagonally to create a diamond pattern. Brush the glaze on liberally so the flavours soak into the meat. Place the ham in a 2½-inch deep roasting pan. Cover with aluminum foil to retain moisture.
 

Roast the ham until the internal temperature reaches 140F, approximately 3 hours. Baste the ham with the glaze a couple of times during roasting. To get a crisp outer layer, you can remove the foil in the last 10 to 12 minutes of cooking and increase the temperature to 400F.
 

Take the ham out of the oven, glaze one last time and sprinkle the parsley on top. Let rest for a few minutes before carving.